EP0520097A1

EP0520097A1 - An improved method and process of distillation/deodorisation of oils, fats and fatty acids

Info

Publication number: EP0520097A1
Application number: EP91305554A
Authority: EP
Inventors: Mulshankar Saburbhai Panchal
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-06-19
Filing date: 1991-06-19
Publication date: 1992-12-30
Anticipated expiration: 2011-06-19
Also published as: DE69114276T2; DE69114276D1; EP0520097B1

Abstract

An improved method and process of distillation and deodorisation of oils, fats or fatty acids is disclosed. It comprises the steps of first pre-heating (90) a feedstock, further preheating (20) the feedstock, then cascading (80) the feedstock in a series of processing tray members, followed by cooling the same through a final heat exchange means (90), and then recovering (30) whatever fatty matter remained in the issuing vapours: The movement of the feedstock is achieved under the influence of vacuum. The invention discloses several improvements in the members and apparatus.

Description

TECHNICAL FIELD:

The present invention related to an improved method and process of distillation and deodorisation of oils, fats and fatty acids, particularly in creating a concentric cross flow of the feedstock with shallow weir waterfall formation.

BACKGROUND ART:

Most of the oils, fats and fatty acids contain various impurities, which interfere with their use as edible products or give rise to an unacceptable taste. The removal of these oil-soluble impurities is accomplished in the process of de-gumming, refining, bleaching and deodorisation.
When the oil or fat is heated, the flavour materials start to distil and if the heating is carried out under vacuum, the rate of distillation is increased and the oil or fat is protected from oxidation. Distillation is improved further by passing steam through the oil or fat. Deodorisation may well be described as a steam distillation under high vacuum. The refining step is sometimes referred to as neutralization because the main objective is to remove the free fatty acids, which have developed in the oil. Free fatty acids can be distilled in a current of steam under high vacuum, and at a temperature similar to that used in normal deodorisation of oils, fats or fatty acids. To keep the time of exposure to high temperature to a minimum, stills have been designed to expose only a thin layer of oil or fat or fatty acid to the distillation conditions, giving the maximum distillation efficiency. In order to recover the distillate, the condensation system for the fatty acids and steam must be separated and an efficient high vacuum system installed to give absolute pressures of under 5 mm of mercury. Fatty acids and fatty acid vapours are very corrosive so that the plant must be made in the correct grade of stainless steel.
Refining of oils , fats and fatty acids is done normally by chemical or physical refining either by a batch or a continuous process.
The continuous process was developed to overcome some of the disadvantages of the batch process, giving a more consistent quality,low energy consumption,higher production capacity and efficiency. In the continuou process, the distillation / deodorisation apparatus and the vapour scrubber apparatus are the most critical and the heart of the entire process.
The requirements for vacuum, temperature, stripping steam and the time of exposure depend on the liquid head pressure exerted on volatile fatty acid molecules.
In the prior art designs by several manufacturers, an attempt is made to reduce the liquid head pressure by employing small size or volume apparatus and tray members. Even with this adaption, the liquid head pressure remains considerable, therefore requiring high processing temperture and energy. The longer exposure time of the oils or fats or fatty acids to high temperature results in slight deterioration of the quality of the oil or fat or fatty acid.
In the prior designs, change of feedstock causes problems inter-mixing of feedstocks, resulting in the loss of expensive raw materials and longer processing time. After considerable operation at high temperature, the fatty matters polymerise and form a thin film. This thin layer of film on the heat conducting surfaces of all coils reduces the heat transfer efficiency due to the insulating characteristic of this polymerised film. The quality of the finished product is also lowered due to the contamination by the polymerised trace materials.
In the prior art designs, cleaning solution is circulated to clean all apparatus, instead of using the same product to be processed. During the circulation, stripping steam is applied together with the cleaning solution. In this method, the introduction of stripping steam reduces the concentration as well as the effectiveness of the cleaning solution. Surfaces at high location is not wetted properly and manual scraping and cleaning are required. The greatest cost factors in deodorisation are steam consumption and loss of oil or fat or fatty acid.
The volatile fatty matters removed from the distillation / deodorisation apparatus may pollute the barometric water upto 30 ppm level and this poses an environmental problem. The prior art designs employ scrubbing of vapours by a packed column or a spray system, or a combination of both. The amount of fatty matter escaping the system is still considerable.
Another prior art design employs the injection of water into the vapour line to the scrubber. This cools the vapours and condenses the fatty matters from the vapour, but this system affects the vacuum system, requiring a higher ejector steam consumption to maintain a bigger size vacuum system.

SUMMARY OF INVENTION:-

The principal objects of the present invention is to minimize the liquid head pressure exerted on the fatty matter molecules to a negligible level, and to provide a large surface area to the ebullation process, and to provide sufficient agitation or kinetic energy to the molecules for efficient ebullation of the volatile fatty matters, and to reduce the time of exposure of the feedstock to high temperature. Another object of the invention is to facilitate an easy and quick change of the feedstock, with negligible intermixing.
Another object of the invention is to provide a cleaning in-place (CIP) cleaning system for efficient cleaning. Yet, another important object of the invention is to improve on the recovery of the fatty matters in the issuing vapours by bubbling the vapours through a perforated member submerged in a sump. By further improving on the efficiency of the spray system and the column packing system in an improved vapour scrubber apparatus, the vapours can be cooled to optimum level, thereby enhancing the overall system efficiency.
In order for the present invention may be more readily understood, the following description is given, by way of example only, with reference to the following drawings, in which:-

Figure (1) shows the overall sectional view of the invention, revealing the relative assembly of the various components making up the invention;
Figure (2) shows the cross-sectional views of an external heat exchanger apparatus and an improved distiller/deodorizer apparatus:
Figure (3) shows the cross section view of a processing tray member in an improved distiller/deodorizer apparatus, fitted with a multi-port drain valve mechanism;
Figure (4) shows the cross section view of an improved vapour scrubber apparatus;
Figure (5) shows the cross section view of an external heat exchanger apparatus to the improved distiller/deodorizer apparatus.

DETAILED DESCRIPTION

Referring to Figure (1), an improved distiller/deodorizer apparatus (10) is substantially of a vertical cylindrical shape having a series of processing tray members (80) and a final stage heat exchange means (90). This basic unit (10) must be vacuum tight connected to a high vacuum lines (35) and is preferably all welded construction to ensure the absence of leaks. A feedstock of oil or fat is first pre-heated through the final stage heat exchange means (90) in the distiller/deodorizer apparatus (10), and then an external heat exchanger means (20). An economizer member (60) is installed to heat water by making use of the heat from the flue gas generated from a heater member (50). The heater member (50) supplies the heating medium to the external exchanger apparatus (20).
The volatile fatty vapours issuing from the distiller/deodorizer apparatus (10) is fed under vacuum to a vapour scrubber apparatus (30). The scrubber apparatus (30) which, installed in the vapour main (70), will wash the vapours with a spray of fatty acid, condensing the distillate and trapping droplet carry over, allowing only a fat-free vapour to pass to the high vacuum set (not shown).
Now referring to Figure (5), the external heat exchanger apparatus (20 is of a cylindrical shape, with a series of circular heating coils (21) connectable in a horizontal spiral fashion to the inlet (22) and outlet (23) header nozzle members, through which the heating medium flows. Inside the heat exchanger apparatus (20) is positioned a concentric channel (25) with a closed bottom (24) attached to the inside wall. The heating coils (21) are placed in the cavity of the this concentric channel member (25). The feedstock to be further heated is supplied via an inlet (310) at the bottom section (26) of the concentric channel (25), and flows upwardly across the heating coils (21) in counter current flow direction to that of the heating medium. The heat feedstock moves upwards under the influence of vacuum (27) supplied at the top end of the exchanger apparatus (20), and cascades down a central opening (28) defined by the central partition (25) in the form of thin concentric film, and into an outlet pipework (29) connectable to an improved distiller/deodorizer apparatus (10). A drain valve (311) is placed between the inlet (310) and the outlet (29).
Referring to Figure (2), the improved distiller / deodorizer apparatus (10) is of a vertical, cylindrical shape, with a series of processing tray members (80) and a final stage heat exchange means (90) installed inside the vessel. The size and the number of the processing tray members (80) depend on the capacity of the distillation and deodorisation required. The bottom section of the vessel is flat-bottomed and a multi-port drain valve mechanism (100) is installed at the bottom end of the vessel. Three channel members are shown inside at the bottom end of the vessel. The number of channel member also depends the capacity and type of the feedstock. In each concentric channel is interposed a concentric partition member (91), slightly raised from the bottom and leaving a space for fluid communication within the channel member. These partition members (91) allow the feedstock to flow in a U-shaped direction, instead of flowing by the shortest path. The feedstock will then cascade inwardly into the next innermost channel member. This sequence is then repeated. In this final stage heat exchange means (90), a series of heating coils (92) is placed inside the cavities defined by the concentric channel members and the partition members (91). The feedstock is pumped from the inlet pipe (14A) at the bottom of the vessel into the innermost coil, flowing outwardly concentrically inside the into an outlet pipe (16) at the side of the vessel connectable to the external heat exchanger apparatus (20).
After the step of distillation / deodorisation is completed, the processed feedstock flows by gravity from the processing tray members (80) downwardly into an inlet pipe (18) which is connectable to the outmost channel member of the tray member (80). Here, the processed feedstock flows from the outermost channel member inwardly and concentrically to the innermost channel member. Finally, the processed feedstock exits the vessel through a funnel of a outlet riser pipe (15).
Preferably the heat transfer mode is achieved through a counter-flow arrangement. In this way, the outgoing processed feedstock is used to pre-heat the incoming feedstock, without inter-mixing.
In order to maintain a constant temperature heat during the process of distillation / deodorisation, a heating coil means is provided at each outermost channel member of each processing tray member. The inlets of the coils are connectable to a common inlet header member (13) and the outlets are connectable to another common header member (14) for circulating the heating medium.
Referring to Figure (3), each processing tray member (80) is having a multiple concentric channel ( 87, 88, 89 ) member arranged with a stepped slopping bottom (A, B, C). The feedstock flows by gravity from the outermost channel member inwardly and concentrically. The number and size of the processing tray members (80) depend on the type of the feedstock and the capacity of the processing plant. In each channel member, a baffle plate member (86) is provided slightly raised from the stepped bottom, so that the feedstock will flow at the base of the baffle plate member (86) in a U-shaped manner upward, and while rising up in the second concentric ring (82) defined in the first channel member (89), the feedstock cascades in a shallow weir waterfall. Some of the feedstock will impinge (84) on the upper end of the next baffle member (86) in the next channel member, while the majority of the feedstock flows down the third concentric cavity (83) defined in the second tray member (88). Turbulence and shallow weir reduced the liquid head pressure exerted on the fatty acid molecules. This cascading and impinging action takes place a couple of times, until the feedstock is exited to the next processing tray member (80).
Also provided at the base of each channel member is a series of perforated coil (5), which allows high pressure steam from inlet pipes (312) to escape. The flow of this stripping steam runs in counter direction to the downward flow of the feedstock at the cascading points. Fatty molecules become very volatile in the shortest possible time and with minimum energy consumption.
A plurality of down comer pipe (6) with a funnel is connectable to the innermost channel member (87) and allows the processed feedstock to move on to the next processing tray member (80). Preferably the number of the down comer pipes is four per tray member and they are placed at a equi-distanced interval on the same circumference. Also a multiple port drain valve mechanism (200) is connected to the base of each tray member (80) in a sloping fashion and connectable to the outgoing pipework to the next processing tray member. To facilitate a quick and easy drainage of the feedstock, preferably a conical valve and a valve seat arrangement is provided for at each drain connection. All the conical valves are operable by a common spindle means either manually by hand wheel mechanism or automatically by actuator means. The flange connexion members (8) & (9) are provided for easy assembly and maintenance of the drain valve mechanism. Each drain valve mechanism is connectable to a drain pipe member (6A) for draining the feedstock to the outermost channel member of the next processing tray member.
This multiple port drain valve mechanism (200) is preferably provided at each processing tray member (80), and the final stage heat exchange means (90) inside the distiller / deodorizer vessel (10). The number of ports depend on the number of the channel members in each respective tray member. Preferably, each drain stem has either a gland sealing stuffing box mechanism or maintenance free bellow seals to prevent leakage. Some volatile fatty vapour will condense underneath the bottom (A.B.C.) of the tray member (80) and because of the slope, the condensed liquid will run off the circular edge of the central ring opening (F) in each tray member. It is important that the diameter (E) of this central ring opening (F) is substantially smaller than the inner diameter (D) of the innermost channel member. This way, the condensate dripping from the central ring opening (F) will fall directly into a collection pot member (12) at the bottom of the distiller / deodorizer vessel. (Figure 2) The condensate does not fall into the next lower tray member and is prevented from contaminating the product in the next tray member.
A level controller means is provided in a collection pot member (12) to discharge the distillate intermittently for recycling via outlet (313). Again referring back to Figure (1), a circumferential spray nozzle ring member is provided over each processing tray member as well as the final stage heat exchange mean (90). Each of these spray nozzle ring members is connectable to a common header member located in the central opening of the distiller/deodorizer vessel (10). High pressure cleaning solution (300) is sprayed to clean the internal surfaces, avoiding manual scraping and cleaning. As the strength of the cleaning solution is maintained, it is not required to replenish the cleaning solution.
Reverting to Figure (1), a balanced vacuum is supplied to both ends of the distiller/deodorizer vessel (10) through a pipe work (70) of substantially larger diameter. This pipework (70) is connectable to an improved vapour scrubber member (30).
Referring now to Figure (4), an improved vapour scrubber member (30) is also vertically cylindrical in shape. The scrubber member (30) comprises a bottom section (31) as a sump for re-circulation liquid, a middle section (32) as a spray section for washing and cooling of vapours, and a top section (33) as a section with column packing for and wash liquid distribution system for final scrubbing of the vapours. These sections may be arranged in series as an individual item apparatus or in a different sequence.
The vapours from the improved distiller / deodorizer vessel (10) enters the improved vapour scrubber member (30) at the inlet connection member (70) and escapes through a perforated distribution box member (71) submerged in a sump (72). The liquid level in the sump (72) is adjustable by a level control means (73) for adjusting the hydrostatic pressure head on the vapour distribution box (71). The vapours coming from the distiller/deodorizer vessel (10) are entrained with a mist of fine fatty matter particles and volatile fatty vapours. As the vapour is bubbling through the perforated distribution box (71), the mist particles are trapped and condensed. The remaining vapours is washed in the spray section (32).
The wash liquid from the sump (72) is pumped through a cooler member (75) to spray nozzles (76) and distribution header member (77) above the column packing section (33). In the spray section (32),the vapour is also cooled by the spraying liquid to an optimum temperature with the help of a temperature sensor (78), a temperature controller and flow distribution valve (79). By cooling the vapours and the spray system further, volatile fatty vapours condense. The remaining trace fatty vapours are finally scrubbed in the column packing section (33) where the liquid is fed into a distribution channel member (77) overflowing on a perforated plate member for uniform distribution of wash liquid over the packing material (36).
Since the vapour is having a negligible loading on the system, the packing section (33) can achieve the highest efficiency. The uncondensable vapour and steam sucked out by a high vacuum system through a demister member (34) which prevents the carrying-over of wash liquid particles. By this method of bubbling the vapours through a sump (72), the major load is reduced on the system. The vapour temperature in the spray section (32) also cooled to an optimum level. This triple-stage vapour scrubber member (30) can achieve the highest efficiency.

Claims

An improved method and process of distillation a deodorisation of oils, fats or fatty acids utilising the passage of steam there through characterised by:-the step of first pre-heating a feedstock of oils, fats or fatty acids through a final stage heat exchange means (90) in an improved distiller / deodorizer apparatus (10); the step of further preheating the feedstock in an external heat exchanger apparatus (20);
the step of cascading the feedstock in a series of processing tray members (80), achieving a shallow weir waterfall effect at each cascade with the formation of a cross flow with respect to the upflow of steam there through the step of cooling the feedstock at the final stage heat exchange means (90) in the improved distiller/deodorizer apparatus (10), without intermixing; the step of recovering any fatty matter in the issuing vapours from the distiller/deodorizer apparatus (30) by exiting the vapour through a perforated ring member (71) into a liquid sump (72) in an improved vapour scrubbe vessel (30); and the step of moving the feedstock under the influence of balanced vacuum (70) attached to the ends of the improved distiller/deodorizer vessel (10)
An improved method and process of distillation and deodorisation of oils, fats or fatty acids as claimed in Claim (1) in which each processing tray member (80) is equipped with a multiple concentric channel members (80) arrangement comprising of baffle plate members (86), slopping bottom design (A, B, C) and connection members (6, 6A), the flow of the feedstock being cascading inwardly or outwardly down the distiller / deodorizer vessel (10).
An improved method and process of distillation and deodorisation of oils, fats or fatty acids as claimed in Claim (1) or (2) in which the series of processing tray members (80) can be housed in a single vessel or a plurality of vessels.
An improved method and process of distillation and deodorisation as claimed in Claim (1) or (2) in which one multiple port drain valve mechanism (100, 200) is installed below and along each processing tray member (80), and the bottom of the improved distiller/deodorizer vessel (10).
An improved method and process of distillation and dedorisation as claimed in Claim (1) or (2) in which the series of processing tray members (80) are being housed in one vessel, and the central exit opening (E) of a first processing tray member is substantially smaller than the central entry opening (D) of a second processing tray member below the first tray member and subsequent to the flow of the feedstock.
An improved method and process of distillation and deodorisation as claimed in Claim (1) in which the external heat exchanger apparatus (20) is equipped with a concentric channel (25) arrangement, containing heating coil members (21), with the feedstock entering at the bottom section of the channel member (25), and rising up while being heated, and cascading / overflowing downwardly and concentrically into an outlet (29) or a collection chamber member in the improved distiller/deodorizer vessel (10),the heat transfer being achieved preferably by a counter flow arrangement.
An improved method and process of distillation and deodorisation as claimed in Claim (1) in which the final stage heat exchange means (90) comprising concentric channel members, concentric partition members (91), and heat exchange coil (92) members, whereas the feedstock moves through inside the coil members (92), while the processed feedstock moves cross - wise through each concentric channel member and partition member (91) in a longer flowpath, by an unfilling and cascading action respectively.
An improved method and process of distillation and deodorisation as claimed in Claim (1) or (3) in which a cleaning-in-place (CIP) system (300), comprising a series of nozzle spray ring members connectable to a supply header for a high pressure chemical recirculation, is installed inside the improved distiller / deodorizer vessel (2), the cleaning medium being preferably high pressure chemical.
An improved method and process of distillation and deodorisation as claimed in Claim (1) or (3) in which the feedstock moves downwardly under the influence of balanced vacuum (70) connected to the ends of the distiller / deodorizer vessel(s) (10).
An improved method and process of distillation and deodorisation as claimed in Claim 1) in which the improved vapour scrubber system (3) comprising a sump system (72), a spray system (76),and a column packing system (36) housed in one vessel or separately in a plurality of vessels.
An improved method and process of distillation and deodorisation as claimed in Claim (1) or (10) in which the spray system (76) in the vapour scrubber system (3) is equipped with temperature control means, and flow diverting valve means (79) for optimum cooling of the vapour.